The DA predicted transmitting ability (PTA) represents the expected resistance of an animal’s offspring to displaced abomasum in a herd with average management conditions. Evaluations are expressed in percentage points of resistance above and below the breed average. Larger, positive values are more favorable.
Resistance to Displaced Abomasum (DA)
DA measures the resistance to Displaced Abomasum
Benefits of Trait
Introduced in April 2018 and April 2020, genetic and genomic evaluations for resistance to displaced abomasum (DA) are provided for Holstein and Jersey males and females, respectively. Evaluations are expressed in percentage points of resistance above and below the breed average.
- Displaced abomasum is a serious health event, often requiring veterinary intervention and surgery.
- Displaced abomasum has the highest direct cost of the six new health traits at $197 per case. This does not include any associated costs such as decreases in production and fertility1,2 already accounted for in Net Merit.
- The significant genetic component of this trait indicates that producers can select animals less likely to have displaced abomasum.
Resistance to Displaced Abomasum (DA)
Percentage points
The average resistance rate is equal to 97.9% in U.S. Holsteins. The resistance rate is equivalent to the incidence rate subtracted from 100.
Daughters of a Holstein bull with a DA PTA of +1.0% are expected to have an average resistance rate to displaced abomasum of 99% (assuming the breed average resistance is approximately 98%). Daughters of a Holstein bull with a DA PTA of -2.0% are expected to have an average resistance of 96%. Daughters from the bull with PTA -2.0% are expected to have four times the number of cases of displaced abomasum as daughters from the bull with PTA of +1.0%
| Breed | Mean GL for Cows | Mean GL for Heifers | Mean GL for the current base year (2010) |
| Holstein | |||
| Jersey |
Holsteins: April 3, 2018
Jerseys: April 7, 2020
DA is currently available for Holsteins and Jerseys. As more health data become available, evaluations can be provided for additional breeds.
DA is included in selection indices for Holsteins and Jerseys as part of the Heath $ sub-index.
Estimated heritability is 1.1% for resistance to displaced abomasum (observed scale).
Young genomic bulls are expected to have reliabilities averaging 42% for resistance to displaced abomasum, and progeny tested bulls are expected to have genomic reliabilities averaging 47%. As additional data is accumulated, reliabilities will increase.
| Breed | Average Reliability for GL of Young Genotyped Bulls by Breed |
| Holstein | |
| Jersey |
The largest significant (P < 0.05) correlation with PTA for resistance to displaced abomasum was with PTA for livability at 0.47. This implies that animals that experience displaced abomasum are much less likely to survive in the herd. Additional significant correlations were 0.35 with productive life PTA, 0.32 with daughter pregnancy rate PTA, and 0.28 with cow conception rate PTA.
CDCB DA evaluations were developed using producer-recorded data collected through Dairy Herd Information (DHI) affiliates from herds across the U.S. Strict editing was applied to ensure only the most reliable data was included for the development of genetic evaluations. The edited data included a total of 1.8 million DA records from 1 million cows. These health records are used in conjunction with lactation data available in the national cooperator database, stewarded by CDCB.
The standard deviation (variation) for DA PTA is 1.0%. Because 1 and 2 standard deviations normally include 68% and 95% of observations, respectively, we assume about 68% of bulls will have a DA PTA between -1.0% and +1.0% while 95% of the bulls will range from -2.0% to +2.0%.
DA PTAs range from 4.0 percentage points below to 1.6 percentage points above average in evaluated Holstein bulls born since 1990 with reliabilities ≥90% (December 2017).
Pre-release analysis indicates the active AI Holstein sires in December 2017 (614 bulls) range from -1.0% to +1.1%, with the average at approximately 0 percentage points.
Future Development
In the future, further model improvements and development will be researched and tested. This may include the development of a multi-trait model that incorporates multiple metabolic disorders.
Related Publications
Donnelly, M. R., A. R. Hazel, B. J. Heins, & L. B. Hansen, 2018. Health treatment cost of Holsteins in 8 high-performance herds. J. Dairy Sci. (in preparation).
Liang, D., L.M. Arnold, C.J. Stowe, R.J. Harmon, & J.M. Bewley, 2017. Estimating US dairy clinical disease costs with a stochastic simulation model. J. Dairy Sci. 100(2): 1472–1486.
Information last updated March 2018.